Granular coated article



0- H. P. KIRCHNER ET AL 2,137,743

GRANULAR COATED ARTI CLE Original Filed April 5, 1934 INVENTORS HENRY P.KIRCHNER BY. CHARLES E WOODDE LL ATTORNEY.

Patented Jan. 23,

um'rap STATES PATENT OFFICE Niagara Falls, N. Y., asslgnors to eCarborundumCompany, Niagara Falls, ..Y., a corporation of DelawareContinuation of application Serial No. 719,173, April 5, 1934. Thisapplication April 28, 1938,

Serial No. 204,!60

3 Claims.

This invention relates to granular coated articles and more especiallyto granular coated discs.

This application is a continuation of our 00- pending application SerialNo. 719,173, filed April 5, 1934. ,7

Abrasive coated discs have heretofore ordinarily been made by formingthe backing of a combination of cloth and fibre, such as vulcanizedfibre, and attaching thereto abrasive granules by means of an adhesivesuch as glue or the like. Discs made with .flbre and cloth backings aresoon cracked, twisted, or torn, and otherwise prematurely rendered unfitfor use. Furthermore, the use of fibre and cloth backings gives theproduct a, warped appearance and prevents it from being applieduniformly and eiilciently to the surface to be ground or polished.

It is an object of the present invention to provide a new and improvedgranular coated article that will overcome these and otherdisadvantages, and to provide a method of making the same in aneflicient and economical manner. I

Fig. 1 is a plan view of a circular abrading .disc;

Fig. 2 is a section thereof on the line 2-2 of Fig. 1; and

Fig. 3 is a diagrammatic representation of a cut-off part of a disc inuse illustrating the manner of use.

According to one modification of our invention, fabric such as paper orcloth 2 is attached to a metal backing I, such as steel, brass, copper,aluminum or the like, by means of an adhesive 3. The metal to be used isfirst roughened on one side or, if desired, on both sides, bysand-blasting, chemical etching or knurllng, to provide a suitablesurface for receiving and holding the adhesive. The roughened surface isthereafter washed with a solvent or similar material that acts tocleanse it and the fabric is then attached either to one or bothsurfaces of the metals, as

may be desired, by means of an adhesive that will adhere to both metaland to paper or cloth. We prefer to use, as an adhesive for thispurpose,

' a. partially vulcanized ,latex in solution, such as Vultex, althoughsulphonated rubbers of the Vulcalock type, soluble rubbers and resincements can also be used. Thefabric is then given a coating of adhesivesuch as glue, to which is applied, by any method known in theart, acoating of granular material l such as silicon carbide, emery, etc.

According to another modification of our invention, one surface of thefabric 2 is first coated with abrasive granules l and the uncoated sideis attached, by means of an adhesive 3, to the previously roughenedsurface of the metal backing l. The application of the abrasive granulesto the fabric before mounting the fabric on the metal is preferred inthe manufacture of de- 5 pressed center discs, although it is to beunder!- stood that the time and method of applying the granular coatingto the backing is a matter of choice and convenience and does notappreciably affect the quality of the article produced.

. As anexample of one modification, one surface of a sheet of springsteel approximately .032" thick is sand-blasted to roughen it.Immediately. thereafter, it is cleansed with benzol, and a thin film ofa solution of vulcanized latex, such as Vultex, is applied thereto. Theuncoated side of the fabric that has been coated on one side withaluminous abrasive material, is pressed firmcoated surface of the metalbacking by means -of a soft rubber roller, or the like, and held in thisposition until the latex has thoroughly dried. The metal sheet with thegranular coated fabric adheslvely attached to one face thereof is thenready to be cut into the granular coated article covered by thisinvention.

In the manufacture of the granular coated articles of this invention,variations in the above procedure may be made when it is found expedientto do so. For example, in the caseof .depressed center discs theoperation of stamping the discs out of the metal sheet, depressing thecentersthereof and punching supporting holes there in is eitherperformed before the metal sheet has been roughened and cleansed, or itis done after the granular coating has been applied, to the metalbacking.

The product of the present invention overcomes the numerousdisadvantages now experienced with the granular coated articles hereto--fore used, in that the backing here provided is flexible, resilient andstrong, as well as having the property of preventing warpage in thefinished article.

As illustrated diagrammatically in Fig. 3, when these discs are usedthey are applied to the work at an angle and under pressure so that theycontactthe work points over an appreciable area at and near theperiphery. The part of the disc which is in contact'with the work isnecessarily bent out .of the plane of the rest of the disc and as thedisc rotates thisbent portion again assumes a plane position normal tothe axis of rotation of the disc. As a result of this method ofapplication, the outer portion of the disc is being continually flexedand distorted out of the plane surface where it is applied to the workpiece and then caused to return to its original plane surface by theresilience of the disc. In order to obtain the requisite pressure of theabrasive grains against the material being abraded, it is necessary thatthe discs have an appreciable amount of stiffness or resistance toflexure. At the same time, the discs must have the capability ofwithstanding repeated flexing and distortion which follows from theiruse in the manner described.

Because of the repeated flexing of the composite article, the adhesiveused. to attach the abrasive coated fabric to the metal backing must becarefully selected. If ordinary glue is used for this purpose, the gluecracks because it does not have the required flexibility to withstandthe repeated flexing. As was indicated, we use a flexible cement forthis purpose including specially proportioned rubber compositions,flexible resins such as special alkyd resins formed by condensing apolyhydric alcohol with sebacic or adipic acid, or resins which arenormally somewhat stiff but flexibilized by the inclusion of suitableplasticizers according to methods well known in the art.

Heretofore, it has been necessary to use supporting pads with the discsto supply the requisite support to fibre and cloth backed discs, and toadd resiliency thereto, in order that the discs might be subjected topressure and flexing without being cracked. Regardless of the provisionof supporting pads, the efllciency of the discs has been low because thevery nature of the work for which they are intended requires continualflexing and bending of the discs, and when the fibre and cloth backeddiscs are repeatedly flexed and bent, they crack and are renderedinoperable prior to the wearing away of the abrasive thereon. Withoutsupporting pads, these discs are practically useless.

On the other hand, the product of the present invention is one that hasa high degree of flexibility, permitting it to be flexed and even bentback upon itself innumerable times without cracking or otherwise beinginjured in any way. It has exceptional strength, and this, coupled withits capability of yielding to pressure while resisting bending to theextent necessary to exert the required pressure on the work, permits itto act as a supporting pad of itself without the necessity of anyadditional or auxiliary supporting means. It can not be torn easily, andthus the article is capable of maintaining the sustaining lots or holesby means of which the discs are attached to the drive shaft. 7

This improved disc is especially advantageous where it is used to cleanout channels or corners, as for example, in the finishing or polishingof automobile bodies. This is due to the fact that when the abrasive onthe outside edge, which contacts with the surface, wears off, theoutside edge of the disc maintains its stiffness. Such is not the casewith flbre and cloth backed discs as the wearing away of the abrasive onthe edges causes the discs, even when supported by the usual supportingpad, to bend over freely and renders them incapable of working down intothe comers or channels, or the like.

Articles of the present invention are not affected by atmosphericconditions and moisture encountered during the manufacture and use ofthe abrasive articles does not have any deleterious effect thereupon.

The provision of a granular coated article which does not warp is asubstantial improvement in the art inasmuch as difiiculty has heretoforebeen experienced with warpage in discs. Fibre and cloth backed discsusually warp on two opposite sides and when used. this warpage causesintermittent deflection of the disc from the surface to be ground at arate of two deflections per revolution of the disc. In consequencethereof, this deflection causes uneven grinding of the surface to befinished, and uneven wearing of the disc. Discs that do not warp have agreater area of contact than those that do warp. In addition, theinherent elasticity of the discs made according to this invention givesa more constant work pressure.

From the standpoint of cost of manufacture,

metal backings for abrasive discs are a material advance in the art. Tosecure the equivalent strength and weight in a fabric or cloth backingof a very thin sheet,of metal, the fabric must be very heavy, and aheavy sheet of fabric is decidedly more expensive than a thin sheet ofmetal. They are further of advantage because the discs may be accuratelystamped or out out from the metal that has been coated with paper orcloth and granular material without cracking the adhesive. I

It is not intended that the scope of our invention shall be limited butshall be commensurate with the spirit of the appended claims.

We claim:

1. A granular coated article comprising a flexible disc of continuoussheet spring metal having an abrasive coated fabric attached thereto bya flexible resin cement, said disc having sufllcient flexibility topermit it to be flattened over an appreciable area at and near theperiphery when applied to a workpiece at an angle under pressure andsuflicient resilience to cause it to return to a plane surface when thepressure is removed, and said cement having suflicient flexibility topermit the disc to be repeatedly flexed without impairing the attachmentof the fabric to the metal.

2. A granular coated article comprising a flexible disc of continuoussheet spring metal having an abrasive coated fabric attached thereto bya flexible cement, said disc having suflicient flexibility to permit itto be flattened over an appreciable area at and near the periphery whenapplied to a workpiece at an angle under pressure and suflicientresilience to cause it to return to a plane surface when the pressure isremoved, and said cement having sufiicient flexibility to permit thedisc to be repeatedly flexed without impairing the attachment of thefabric to the metal.

3. A granular coated article comprising a flexible disc of continuoussheet spring metal having an abrasive coated fabric attached thereto bya flexible rubber cement, said disc having suflicient -flexibility topermit it to be flattened over an appreciable area at and near theperiphery when applied to a workpiece at an angle under pressure andsuiflcient resilience to cause it to return to a plane surface when thepressure is removed, and said cement having sufficient flexibility topermit the disc to be repeatedly flexed without impairing the attachmentof the fabric to the metal.

HENRY P. KIRCHNER. CHARLES E. WOODDELL.

